Array和ArrayList的自定义排序问题

首先定义一个Book类:

namespace ArrayListSort
...{
    class Book:IComparable<Book>
    ...{
        private string _bookname;
        private string _bookcategory;
        public double _price;

        public string BookName
        ...{
            get ...{ return _bookname; }
            set ...{ _bookname = value; }
        }
        public string BookCategory
        ...{
            get ...{ return _bookcategory; }
            set ...{ _bookcategory = value; }
        }
        public double Price
        ...{
            get ...{ return _price; }
            set ...{ _price = value; }
        }

        public Book(string bookname, string bookcategory, double price)
        ...{
            _bookname = bookname;
            _bookcategory = bookcategory;
            _price = price;
        }

        IComparable 成员#region IComparable<Book> 成员

        public int CompareTo(Book other)
        ...{
            return (BookName.CompareTo(other.BookName));
        }

        #endregion
    }
}

以下定自定义排序类PriceDownClass来实现IComparer

 

namespace ArrayListSort
...{
    class PriceDownClass:IComparer<Book>
    ...{
        IComparer 成员#region IComparer<Book> 成员

        public int Compare(Book x, Book y)

        ...{
            if (y.Price > x.Price)
                return 1;
            else if (y.Price == x.Price)
                return 0;
            else
                return -1;
            //throw new Exception("The method or operation is not implemented.");
        }

        #endregion
    }
}

以下定自定义排序类PriceDownClass来实现IComparer

 

namespace ArrayListSort
...{
    class PriceCompare : IComparer
    ...{

        IComparer 成员#region IComparer<Book> 成员

        public int Compare(object x, object y)
        ...{
            double i = ((Book)y).Price - ((Book)x).Price;
           // double i = y.Price - x.Price;

            if ( i>0)

                return 1;
            else if (i==0)
                return 0;
            else
                return -1;
        }

        #endregion
    }
}

以下为整个程序的唯一入口:

 

namespace ArrayListSort
...{
    class Program
    ...{
        static void Main(string[] args)
        ...{

            Book[] books = new Book[8] ...{ new Book("C#书籍z", "C#", 45.5), new Book("C#书籍f", "C#", 55.8) ,
                                         new Book("Delphi书籍1","Delphi",78),new Book("C#书籍x", "C#", 55.9),
                                         new Book("Asp.net", "Asp.net", 55.8),new Book("Delphi书籍2","Delphi",79),
                                         new Book("C#书籍y", "C#", 60),new Book("C#书籍b", "C#", 80)
            };

            ArrayList a1 = new ArrayList(books);//以books数组为参数构造ArrayList实例 a1;
            Console.WriteLine("Array_排序前的集合排列:");
            DisplayResult(books);
            Console.WriteLine();

            Array.Sort(books);
            Console.WriteLine("Array_按书籍名称排序后:");//Book类已经实现了IComparable接口
            DisplayResult(books);
            Console.WriteLine();

            Array.Sort(books, new PriceDownClass());
            Console.WriteLine("Array_按书籍价格降价排序后:");
            DisplayResult(books);
            Console.WriteLine();

            //a1.Sort();//Book类已经实现了IComparable接口,但不能实现排序
            //a1.Sort(new PriceDownClass());//Array情况下可以排序，不知为什么ArrayList情况下就不行了??
            /**//*
             更改自定义排序类 public int Compare(Book x, Book y) 改为 public int Compare(object x, object y)
             就可以了在ArrayList的自定义排序中应用,更改后的自定义排序类也可用天Array的Sort()方法 
             */
            a1.Sort(new PriceCompare());
            Console.WriteLine("ArrayList_按书籍价格降价排序后:");
            DisplayResult(a1);
            Console.WriteLine();

            Array.Sort(books, new PriceCompare());//
            DisplayResult(books);
        }

        static void DisplayResult(Book[] al) ...{
            foreach (Book book in al)
            ...{
                Console.WriteLine("书名：{0} 价格:{1} ", book.BookName, book.Price);
            }
        }

        static void DisplayResult(ArrayList al)
        ...{
            foreach (Book book in al)
            ...{
                Console.WriteLine("书名：{0} 价格:{1} ", book.BookName, book.Price);
            }
        }
    }
}

    Array和ArrayList在自定义排序类中的区别从上例中可以看出, 对于集合元素为引用类型时,类中实现了IComperable接口,在Array中可直接进行缺省排序Array.Sort(books),但a1.Sort() 不能实现排序;自定义排序类中实现泛型接口时如果确定IComparer<T>的T类型,则此自定义排序类不能用于ArrayList中实现排序.